Uroflowometry Flashcards
Define urodynamics
Measuring the properties of the bladder for diagnostic purposes
Define uroflowmetry
Measurement of flow rate during voiding
Where can uroflowmetry occur
Clinical
Home
Most common method of clinical uroflowmetry
Gravimetric Flowmeter
Gravimetric Flowmeter
- scales to record the mass vs time
- jug and funnel above scales which patient voids into
- in a clinic
- commode
Units of flow rate
Q (m/s)
How to calculate flow rate?
Differentiate voided volume in respect to time
Key parameters that are good to know?
QMAX = Maximum flow rate
Void Time
Area under curve = voided volume
Shapes of graph = different pathologies sometimes
Artefacts of gravimetric uroflowmetry technique?
- waggle artefact = in men if urine stream is waggled around, can change flow rate instead of straight down
- differentiation = noise
- abdominal straining = increasing abdominal pressure, can mask low flow rate caused by obstruction for example
Advantages of Spinning disc flow meter
- to provide faster temporal resolution
- no differentiation = less noise
How does a Spinning disc flow meter work?
- rota turned by an electrical motor
- turned at a constant rpm (revelutions per minute)
- individual voids into motor and urine stream slows the motor
- motor therefore needs more power to turn at same constant rpm against urine stream
- motor draws more current to turn urine = increased electrical current which is proportional to the flow rate
Why isn’t a spinning disc flow meter used anymore?
In practice, advantages of detecting quick changes in flow rate were not clinically useful
Urine drop spectroscopy Method
- urine stream comes down and breaks down into drops
- drops are assumed to be spherical
- camera system measures number and diameter of drops
- this is used to show flow rate over time
Pros and Cons of urine drop spectroscopy
- no differentiation = no noise
- additional problems of cleaning after use
What is the normal QMax?
20ml/s